1. Field of the Invention
This invention relates to the production of phenol and more particularly to a process for producing phenol and acetone from cumene hydroperoxide.
2. Description of the Prior Art
Phenol is an important organic chemical with a wide variety of industrial uses. It is used, for example, in the production of phenolic resins, bisphenol-A and caprolactam. A number of processes are currently in use for the production of phenol but the single process providing the largest proportion of the total production capacity is the cumene process which now accounts for over three quarters of the total U.S. production. The basic reaction involved in this process is the cleavage of cumene hydroperoxide into phenol and acetone: EQU C.sub.6 H.sub.5 C(CH.sub.3).sub.2 OOH=C.sub.6 H.sub.5 OH+(CH.sub.3).sub.2 CO
On the industrial scale, the cumene hydroperoxide is usually treated with dilute sulphuric acid (5 to 25 percent concentration) at a temperature of about 50.degree. C. to 70.degree. C. After the cleavage is complete, the reaction mixture is separated and the oil layer distilled to obtain the phenol and acetone together with cumene, alpha-methylstyrene, acetophenone and tars. The cumene may be recycled for conversion to the hydroperoxide and subsequent cleavage. The phenol produced in this way is suitable for use in resins although further purification is required for a pharmaceutical grade product.
Although the process described above is capable of producing both phenol and acetone in good yields, it would be desirable to find a process which would reduce the need for the product separation and purification steps which are inherent in a homogeneous process and would avoid the need for environmentally hazardous liquid acids.
The heterogeneous cleavage of cumene hydroperoxide (CHP) over various solid acid catalysts has already been reported. For example, U.S. Pat. No. 4,490,565 discloses the use of zeolite beta in the cleavage of cumene hydroperoxide, whereas U.S. Pat. No. 4,490,566 discloses the use of a Constraint Index 1-12 zeolite, such as ZSM-5, in the same process.
U.S. Pat. No. 4,898,995 discloses a process for the coproduction of phenol and acetone by reacting cumene hydroperoxide over a heterogeneous catalyst consisting essentially of a heteropoly acid, such as 12-tungstophosphoric acid, on an inert support, such as silica, alumina, titania and zirconia. Such heteropoly acid catalysts are inherently unstable at temperatures in excess of 350.degree. C.
U.S. Pat. No. 5,908,800 discloses a process for producing a mixed zirconium and cerium oxide useful as a catalyst for reducing nitrogen oxides in automotive exhaust by contacting a liquid mixture of cerium and zirconium compounds with carbonate and bicarbonate under neutral or alkaline conditions to form a precipitate comprising cerium carbonate and zirconium oxyhydroxide, and then calcining the precipitate.
According to the invention, it has now been found that a solid acid catalyst comprising mixed oxides of cerium and a Group IVB metal can exhibit activity and selectivity for cumene hydroperoxide cleavage.